The inventor has identified the following background and related art. Pollution monitoring, and fire protection and suppressant systems may operate by detecting the presence of smoke and other airborne pollutants. Upon a threshold level of particles being detected, an alarm may be activated and operation of a fire suppressant system may be initiated. While the fire itself will cause damage, considerable property damage and also environmental damage may also be caused by operation of the fire suppression system and subsequent removal of the suppressant may be quite hazardous. A detection system, which is sufficiently sensitive to detect an abnormal condition prior to the onset of a fire, is very advantageous as it enables action to be taken at a very early stage before the onset of actual fire conditions. For example, when most substances are heated, even before heating occurs to a point at which a fire commences, emissions will be generated and if these can be detected by a suitably sensitive system, a warning provided at that very early stage may allow the problem to be detected and rectified, or equipment turned off for example, before the fire actually starts.
Air sampling pollution monitoring equipment in the form of aspirated particle detection systems may incorporate a sampling pipe network consisting of one or more sampling pipes with sampling holes, or inlets, installed at positions where smoke or pre-fire emissions may be collected from a region or environment being monitored, which is ordinarily external to the sampling pipe network. Typical configurations for aspirated particle detection systems are shown in FIGS. 1 and 2 in the form of aspirated smoke detection systems 10 and 20, respectively. Air is drawn in through the sampling holes 14, 24 and subsequently along the pipe or pipe network 12, 22 by means of an aspirator or fan (not shown) and is directed through a detector 16 at a remote location. Sampling points in the form of the sampling inlets 14, 24 are located at regions where particle detection is required. These regions are typically distant from the actual detector. Although there are a number of different types of particle detectors which may be used as the detector in a system as outlined above, one particularly suitable form of detector for use in such a system is an optical scatter detector, which is able to provide suitable sensitivity at reasonable cost. An example of such a device is a VESDA® LaserPlus™ smoke detector as sold by the applicant. Optical scatter detectors operate on the principle that smoke particles or other airborne pollutants of small size, when introduced into a detection chamber and subjected to a high intensity light beam, will cause light to scatter. A light detector senses the scattered light. The greater the amount of particles within the sample introduced into the detector chamber the greater will be the amount of light scatter. The scatter detector detects the amount of scattered light and hence is able to provide an output signal indicative of the amount of smoke particles or other pollutant particles within the sample flow.
A difficulty arises in operation of aspirated particle detector systems of the above kind in that as the detector is remote from the sampling point, and the detector effectively detects particles from a number of sampling points simultaneously, it is difficult to ascertain whether any particular sample point is effectively sampling particles from the environment to be protected thus enabling the detection system to be capable of detecting particles. Furthermore, in some circumstances, one or more sampling points may block or be in a state of becoming blocked.
Smoke detectors, which do not use aspirated sampling pipe networks are also susceptible to failure; and are subject to other failure modes such as faulty electronic components. These detectors are commonly known as “point detectors” and often take the form of a detection chamber in a perforated housing located, for example, proximate to the potential site of a fire. The housings are typically protected to some extent from the ingress of dust, lint and insects and the like by a filter, which may comprise a fine mesh or other suitable barrier. These detectors rely on natural air movement through the region or environment being monitored by the detector for particles to enter through the mesh, but these detectors may become ineffective. Such point detectors are often tested in-situ when in operation in the field by enclosing them in a smoke-filled vessel holding a known concentration of smoke thus, ascertaining whether smoke will be detected in the monitored region. If the detector sounds the alarm then the detector is considered operational. Another method is to direct smoke or some other test medium such as a gaseous test material towards the detector to attempt to provoke an alarm.
U.S. Pat. No. 3,693,401 (Purt et al) and Patent Abstracts of Japan No. JP 11-224386 (Hochiki Corp) disclose devices for enclosing a smoke detector in a housing into which a test medium is sprayed and, directing a test gas at a smoke detector, respectively.
In another form of testing, U.S. Pat. No. 5,170,148 (Duggan et al) discloses a device that relies on the activation of a heating element to test the operational status of a fixed-temperature fire detector.
EP patent No 0910055 (No Climb Products Limited) discloses a test device that generates a stimulus by way of a non-contact detector to sense the presence of a smoke detector engaging the test device in order to initiate the test, which may involve the emission of an aerosol or the activation of a heating element. EP 0910055 also discloses a battery powered test apparatus mounted on the end of a hollow elongate member and means forming a battery retainer adjacent the mounting for the apparatus, which obviates the need for electrical cable from a power source, situated with the user, to a housing member located at the upper end of the elongate member for engaging the smoke detector.
However, the above methods are problematic when dealing with aspirated particle detectors. While the above test methods may be appropriate for non-aspirated point detectors, they present difficulties when applied to testing individual sampling points of aspirated detectors. In an aspirated sampling system as described above and shown in FIGS. 1 and 2, the alarm will be raised remotely at the detector, rather than in the region where testing is conducted. Further, producing and applying a test medium accurately in a number of different areas to test multiple sampling points is difficult, and results can therefore be difficult to analyse.
Any discussion of documents, devices, acts or knowledge in this specification is included to explain the context of the invention. It should not be taken as an admission that any of the material formed part of the prior art base or the common general knowledge in the relevant art on or before the priority date of the invention disclosed herein or, any claims defined herein.